The broad range of standard and custom liquid level sensing solutions are designed to manage liquid levels of water, foodstuffs, chemicals and fuels in all sorts of containers and vessels. These float switches utilize reed switches in a stem that are activated by a magnet in a float. With a large range of different materials for stem and float, these are suitable for use in many fluids, including corrosive acids, and can often be used at temperatures of up to +120 °C. Other options include vertical or horizontal mount, assorted fitting methods and external or internal mounting. Multi-level sensors are available as well as cable-suspended versions. A further range of sensors in metal design completes the range and features APEX approved parts.
In many industrial processes, the level of liquids stored in different containers such as tanks or chambers has to be measured. For this purpose, liquid level sensors provide signals that are used to control the production process or for status indication. A magnetic float combined with a reed switch is one of the most reliable and proven technologies for level measurement. This relatively simple design is reliable in the long run without the user having to calibrate the float switch. When selecting a float switch for a liquid level sensing application, several factors such as the materials of float switch and gasket, physical arrangement, electrical performance and cable type must be considered.
Which sensor design is suitable for your application? The answer depends on the physical arrangement of the tank and the possible installation positions as well as on whether the inside of the tank is accessible or not. While the horizontal or side mounting type normally has a fixed housing mounted in a hole in the side wall of a tank and a hinged float attached to the fixed housing, the vertical mounting version (installed through a hole in the top or bottom of a tank) usually features a fixed vertical shaft, along which slides a cylindrical float.
Any possible liquid deposits on the float body must also be taken into account. Accumulations of these deposits over time may cause the float switch to fail. Specially designed float switch types can minimize the effects of this build-up - to find out more please contact us with your requirements.
Choosing the right material for a float switch is very important. If materials are chosen that are not compatible with the liquids and temperatures of the application, parts of the liquid level sensor can be damaged and ultimately the float switch can even fail completely. Depending on the process fluids present in the application, tests with a sample switch may be necessary to ensure compatibility.
Some typical materials for liquid level sensors are nylon (suitable for many oils, diesel, organic chemicals and MEK-based inks), polypropylene (PP, many acids and alkalis, detergents, inorganic and organic chemicals, oils and water), polyphenylene sulfide (PPS, many of the more aggressive chemicals and process temperatures up to +120 °C), Buna/Nitrophyl (many oils, diesel, petrol and water in non-potable applications), D300 foam (PVC, most hydraulic oils and many chemical solutions) and stainless steel (most medical and food applications, chemicals, hydraulic fluids, fuel oils and process temperatures up to +135 °C).
To ensure reliable operation, it is important to fully understand the type of load to be switched and to ensure that the float switch can handle that load. In most cases, the electrical ratings provided in the float switch specifications refer to purely resistive loads - however, if loads with inductive or capacitive components are to be switched, appropriate measures must be taken to protect the contacts against wear and destruction.
Whenever aggressive liquids may spill onto external wiring, particular materials have to be specified for the float switch connection cables – from standard, UL-approved cable types all the way to high-temperature, low-smoke zero-halogen (LSZH) and other specialised materials.
Custom engineered float switches
You can’t find the float switch in our standard range that fully meets your requirements? Get in touch with AMS Technologies to discuss your custom engineered variant. Our suppliers have a solid history of customizing float switches for a wide range if industry sectors including oil, gas & petrochemicals; food and beverage; chemicals and pharmaceuticals; water and wastewater or process manufacturing – and for any type of environment including industrial process control, safe areas, intrinsically safe and hazardous areas (ATEX-certified) as well as WRAS-approved switches for drinking water applications.